The present invention relates to gas generators used to inflate air bags in an automobile occupant protection system and, more particularly, to an improved dual chamber gas generator wherein structural integrity of each chamber is assured by a novel dual crimp.
Inflation systems for deploying an air bag in a motor vehicle generally employ a single gas generator in fluid communication with an uninflated air bag. The gas generator is typically triggered by a firing circuit when the sensed vehicle acceleration exceeds a predetermined threshold value, as through the use of an acceleration-responsive inertial switch.
However, air bag inflation systems utilizing a single gas generator suffer from the disadvantage that the onset pressurization/inflation rate is generally set to provide aggressive initial inflation in order to achieve a particular inflation time related to occupant position. An aggressive onset rate of pressurization becomes problematic in situations where the occupant is out of position. More specifically, rapid onset pressurization of the air bag can cause the air bag to impact against the occupant with enough force to injure the occupant. The airbag volume and inflating capacity are designed to protect both large and small occupants and are generally not variable within the single gas generator. Occasionally, when an air bag utilizing a single gas generator is deployed, smaller occupants, usually children and smaller women, have been seriously injured.
Commonly owned U.S. Pat. No. 5,400,487 discloses an inflation system which overcomes the above problem by utilizing a plurality of gas generators which are controllably ignited to provide a variable inflation profile which can be tailored to any given occupant weight and/or position and for any crash type. While this arrangement dramatically improves the inflation system""s ability to protect an occupant, it does so at significant expense and complexity. The multiple gas generators and squibs add considerable cost to the system, while the firing control circuitry requires sophisticated processors capable of accurately timing the various ignition profiles.
Another proposal, as taught in commonly owned U.S. Pat. No. 5,934,705, is a gas generator having two chambers in a single housing defined by a mechanically retained wall between the ends thereof. Each housing is of a predetermined size that is determinative of the propellant capacity and consequently, of the inflating capability of each chamber. Upon the occurrence of a vehicle collision, depending on the weight of the passenger, either chamber or both may be selectively ignited thereby inflating the protective airbag. However, the structural integrity of such a known dual chamber inflator, may be compromised by failure of the wall separating the chambers when only one chamber is fired.
Therefore, a need exists for a dual chamber gas generator which can produce selective air bag inflation pressurization yet prevent hazardous structural failure of the gas generator.
In accordance with the present invention a gas generator comprises two combustion chambers formed within a single housing. Each chamber may be tailored to meet a desired inflation pressure thereby providing selective inflation pressurization. A partition is disposed within the housing to define the two chambers and is positively retained by a dual crimp in the inflator housing to insure the structural integrity of the chambers. Flame propagation from one chamber to the other is precluded thereby preventing inadvertent ignition of a chamber not activated by the vehicle acceleration sensing system.